1. Field of the Invention
The present invention is directed to a mechanism and to a method for generating a corotron discharge in electrophotographic devices by a wire-shaped corona discharge electrode.
2. Description of the Related Art
U.S. Pat. No. 4,258,258 discloses a device for generating a corotron discharge wherein a wire-shaped corona discharge electrode, which is also referred to as a corotron, is stretched between two end blocks. The end blocks each have a space through which the corona discharge electrode is conducted. At each end, the corona discharge electrode is held in a electrically non-conductive insert and is inserted with these inserts into the spaces in the end blocks.
The fundamental structure of the inserts is a cylindrical element with an inside bore within which the corona discharge electrode is guided and held at its ends. The holder, for example, can be fashioned such that the corona discharge electrode comprises a spherical thickened portion at one end that is seated on the inside bore of the appertaining insert. At the other end, the corona discharge electrode can be seated in a plug pin for an electrical plug-type connector that is provided in the appertaining insert. Another possibility would be to hold the corona discharge electrode with electrically conductive connector screws in the inserts.
Finally, it is also knownxe2x80x94but not disclosed in the above identified United States Patentxe2x80x94to guide the corona discharge electrode by means of metallic terminal elements provided with small inside bores and to fix it therein by pinching.
Given these known possibilities of fastening a wire-shaped corona discharge electrode, which have inside bores for passing the electrode through, basic problems derive from the wire thickness, which lies on the order of magnitude of 1/10 mm in practice.
First, the diameters of the inside bores in the inserts of the type disclosed by the above United States Patent must be correspondingly small, which is involved in terms of manufacturing technology and therefore costly. An involved and, thus, costly manufacture runs counter to an optimally beneficial mass production.
Second, the threading of such thin electrode wires in bores with a correspondingly small diameter is also inherently problematical in view of preventing damage to the electron wire. This is additionally aggravated in that the cutting of wire sections having a suitable length for a corona discharge device produces burrs at the parting locationsxe2x80x94the wire endsxe2x80x94that also make the threading more difficult. All of this opposes a desired automation of the electrode installation or at least makes it more difficult.
A fastening of wire-shaped corona discharge electrodes by pinching in metallic terminal elements is also disadvantageous both in view of the manufacture of the terminal elements with correspondingly small inside bores, of the threading of the electrode wire into the terminal elements as well as the undamaged quality thereof.
The aforementioned problems likewise occur given devices disclosed by U.S. Pat. No. 5,449,906 that fundamentally correspond to the devices of the initially cited U.S. Pat. No. 4,258,258.
What is thereby also critical is that the wire-shaped corona discharge electrode is also fastened in a stretched condition such that, in a electrophotographic device, it proceeds exactly parallel to an image acceptance elementxe2x80x94a photoconductor elementxe2x80x94of the device, this being of great significance for the image quality.
The present invention is based on the object of providing a mechanism and a method with which a largely automated mounting of wire-shaped corona discharge electrodes is possible while assuring that the electrodes are not damaged.
This object is achieved in a mechanism for generating a corona discharge in electrophotographic devices by means of a wire-shaped corona discharge electrode, whereby the corona discharge electrode is stretched between two end blocks, the end blocks respectively contain a space for the acceptance of a respective electrode holder insert, the electrode holder insert contains a rotationally symmetrical electrode receptacle element with an axially parallel electrode receptacle channel in the generated surface as well as a further electrode receptacle channel in an end face, the further channel adjoining the axially parallel channel and residing perpendicularly thereon, and whereby the electrode holder insert has a cap element that, proceeding from the end face containing the further electrode receptacle channel, can be pressed onto the electrode receptacle element with the corona discharge electrode guided in the electrode receptacle channels.
Further developments of the invention are provided by the electrode receptacle channels being fashioned V-shaped. The floor of the channel of the electrode receptacle channel may be fashioned round, the curvature being matched to the diameter of the wire-shaped corona discharge electrode, the floor of the channel lies centrally relative to a diameter of the circular-cylindrical part having the larger diameter, and the further electrode receptacle channel lies in the extension of the electrode receptacle channel. Identically fashioned electrode receptacle elements may be provided at the ends of the corona discharge wire. In a preferred embodiment, the electrode receptacle element comprises a circular-cylindrical part and a conical part having an overall diameter that is smaller compared to the circular-cylindrical part. The cap element may include an inside cone matched to the conic frustum-shaped part of the electrode receptacle element. In one development, the cap element is fashioned as part of a plug-type connector. Specifically, the cap element has a length suitable for an electrical plug-type connector.
In one variation, the electrode receptacle element is manufactured of plastic. Alternatively, the electrode receptacle element is manufactured of a plastic with a fiberglass or carbon fill. A preferred aspect provides that the electrode receptacle element is fashioned of polyether amide. As a further alternative, the electrode receptacle element is manufactured of a metal. For example, aluminum is employed as metal. A softer material compared to the material of the corona discharge electrode may be employed for the cap element. Another feature provides that a metal is employed as material for the cap element, for example, aluminum is employed as the metal.
In another embodiment, the invention provides a mechanism for fastening a wire-shaped corona discharge electrode by means of an electrode holder, whereby the electrode holder comprises an electrode receptacle element with an axially parallel electrode receptacle channel in the generated surface as well as a further electrode receptacle channel in an end face, the further channel adjoining the axially parallel channel, and whereby the electrode holder has an annular cap element that, proceeding from the end face containing the further electrode receptacle channel, can be pressed onto the electrode receptacle element with the corona discharge electrode guided in the electrode receptacle channels.
A method for generating a corona discharge is provided, wherein the method for fastening a wire-shaped corona discharge electrode by means of an electrode holder, includes the following features:
a) placing the corona discharge electrode into an electrode receptacle element with an axially parallel electrode receptacle channel in the generated surface as well as a further electrode receptacle channel in an end face, the further channel adjoining the axially parallel channel,
b) pressing an annular cap element onto the electrode receptacle element and, thus, fixing the corona discharge electrode guided in the electrode receptacle channel can be pressed on.
The method of a further embodiment includes a method for generating a corona discharge in electrophotographic devices by means of a wire-shaped corona discharge electrode, whereby the corona discharge electrode is stretched between two end blocks, the corona discharge electrode is clamped in electrode holder inserts that have a rotationally symmetrical electrode receptacle element with an axially parallel electrode receptacle channel in the generated surface as well as a further electrode receptacle channel in an end face, the further channel adjoining the axially parallel channel and residing perpendicularly thereon, the corona discharge electrode is placed into the electrode receptacle channels of the electrode receptacle element and is conducted around this, and the annular cap element, proceeding from the end face containing the further electrode receptacle channel, is pressed onto the electrode receptacle element with the corona discharge electrode guided therein.